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Overview

Atrial fibrillation is a heart condition that causes an irregular and often abnormally fast heart rate.

A normal heart rate should be regular and between 60 and 100 beats a minute when you're resting. You can measure your heart rate by feeling the pulse in your neck or wrist.

In atrial fibrillation, the heart rate is irregular and can sometimes be very fast. In some cases, it can be considerably higher than 100 beats a minute.

This can cause problems including dizziness, shortness of breath and tiredness. You may be aware of noticeable heart palpitations, where your heart feels like it's pounding, fluttering or beating irregularly, often for a few seconds or, in some cases, a few minutes.

Sometimes, atrial fibrillation doesn't cause any symptoms and a person with it is completely unaware that their heart rate isn't regular.

What causes atrial fibrillation?

When the heart beats normally, its muscular walls contract (tighten and squeeze) to force blood out and around the body. They then relax, so the heart can fill with blood again. This process is repeated every time the heart beats.

In atrial fibrillation, the heart's upper chambers (atria) contract randomly and sometimes so fast that the heart muscle can't relax properly between contractions. This reduces the heart's efficiency and performance.

Atrial fibrillation occurs when abnormal electrical impulses suddenly start firing in the atria. These impulses override the heart's natural pacemaker, which can no longer control the rhythm of the heart. This causes you to have a highly irregular pulse rate.

The cause isn't fully understood, but it tends to occur in certain groups of people (see below) and may be triggered by certain situations, such as drinking excessive amounts of alcohol or smoking.

Treating atrial fibrillation

Atrial fibrillation isn't usually life-threatening, but it can be uncomfortable and often requires treatment.

Treatment may involve:

medication to prevent a stroke (people with atrial fibrillation are more at risk of having a stroke)

medication to control the heart rate or rhythm

cardioversion – where the heart is given a controlled electric shock to restore normal rhythm

catheter ablation – where the area inside the heart that's causing the abnormal heart rhythm is destroyed using radiofrequency energy; you may then need to have a pacemaker fitted to help your heart beat regularly

Atrial flutter

Atrial flutter is less common than atrial fibrillation, but shares the same symptoms, causes and possible complications. Around a third of people with atrial flutter also have atrial fibrillation.

Atrial flutter is similar to atrial fibrillation, but the rhythm in the atria is more organised and less chaotic than the abnormal patterns caused by atrial fibrillation.

Treatment for atrial flutter is also slightly different, because catheter ablation (see above) is considered to be the best treatment, whereas medication is often the first treatment used for atrial fibrillation.